Some option types cannot use an argument --- boolean options that
would set a bit or flag or increment a counter, for example. If
configured in the flag word to accept an argument anyway, the result
is an argument that is advertised in "program -h" output only to be
rejected by parse-options::get_value.
Luckily all current users of these option types use PARSE_OPT_NOARG
and do not use PARSE_OPT_OPTARG. Add a check to ensure that that
remains true. The check is run once for each invocation of
parse_option_start().
Improved-by: Stephen Boyd <bebarino@gmail.com> Signed-off-by: Jonathan Nieder <jrnieder@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>